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Bio ch 18
| Question | Answer |
|---|---|
| feedback inhibition | regulates the production of enzymes and genes |
| what is an operon | a group of genes controlled together under one promoter, transcribed into one mRNA. |
| Operator | part of an operon DNA region where the repressor binds to control transcription |
| in a trp operon what happens when trp is present | trp binds to the repressor and activates it, the active repressor binds to the operator, transcription stops and operon is off. |
| in a trp operon what happens when trp is absent | repressor is inactive, it cannot bind to the operator, RNA polymerase transcribes genes, enzymes are made to produce trp, operon is on |
| in a lac operon what happens when lactose is present | lactose binds to the repressor, causing it be inactive so it doesn't bind to the operator, transcription happens |
| in a lac operon what happens when lactose is absent | the repressor protein binds to the operator, RNA polymerase is blocked, transcription doesn't happen |
| what is differential gene expression | when different cells express different genes which leads to cell specialization |
| histone protein | DNA wraps around histones for packaging and regulation |
| how does histone acetylation affect gene expression | loosens chromatin promoting initiation of transcription, allowing transcription factors to bind. |
| how does DNA methylation affect gene expression | methyl groups condense chromatin, causes decreased transcription |
| what are control elements | DNA sequence binding sites for transcription factors, located ahead of where genes will be transcribed |
| explain what happens in the regulation of transcription | activators, transcription factors and RNA polymerase form a complex and transcription can begin |
| why does short mRNA lifespan help bacteria | allows rapid changes in protein production in response to environmental changes. |
| How does mRNA degradation affect protein production | the faster mRNA is degraded, the less protein it produces |
| how are proteins targeted for destruction | their marked with an ubiquitin and are degraded by a proteasome and recycled into protein fragments |
| What molecule to miRNAs bind to? | mRNA |
| What is the role of miRNA? | prevent genes expression by blocking translation or causing target mRNA to degrade. |
| explain how miRNAs are formed, how dicer is involved and how miRNAs work. | 1. is processed by enzymes (a miRNA transcript folds into a hairpin structure (base pairing). the enzymes dicer cuts it into a short double stranded mirna) 2. binds to target mRNA 3. inhibits gene expression |
| how do cytoplasmic determinants lead to differential gene expression | as the zygote divides via mitosis, cells contain diff cytoplasmic determinants which activate diff genes in diff cells leading to differential gene expression. |
| whats induction, how does it lead to cell differentiation? | when signal molecules from nearby cells trigger signal transduction pathways that activate diff genes, leading to cell differentiation into specialized cell types. |
| what's determination and what impact does it have on a cell, how does it give rise to tissue specific cells | its when a cell becomes committed to developing into a specific cells type once determined, diff genes are turned on/off |
| what are egg polarity genes | maternal genes that establish the body axes in early development. |
| difference between an oncogene and a proto-oncogene | proto- normal growth gene, regulates cell growth/division oncogene- mutated/ overactive that causes uncontrolled cell division |
| explain how translocation causes cancer | moves oncogene near strong promoter causing overexpression |
| what are tumor suppressor genes and what do they do | slow cell division, repair DNA damage and trigger apoptosis |
| explain the multistep process of cancer development? | 1. mutation in tumor suppressor genes = small benign growth. 2. more mutations in proto-oncogenes = growth grows larger 3. loss of tumor suppressor genes = uncontrolled cell growth 4. cells= malignant cancer cells- invade surrounding tissue. |
| how do e coli respond in the gut of humans if tryptophan is lacking in the human diet | turns the trp operon on, repressor protein becomes inactive without tryptophan and cannot bind to the operator, RNA polymerase transcribes genes and enzymes are produced to synthesize tryptophan |
| inducible vs repressible operon | inducible- turned on by substrate repressible- turned off by product |
| what does an activator protein do | helps RNA polymerase bind which increases transcription |
| whys a repressor protein needed in an induce operon | the operon Is off because the repressor is active by default and bound to the operator blocking transcription, the repressor ensue genes are only expressed when needed, when an inducer binds, it inactivates the repressor allowing transcription to occur |
| explain an inducible operon | normalling off because the repressor is active and blocks transcription. when an inducer (like lactose) binds to the repressor it inactivates and transcription turns on |
| explain a repressible operon | normally on because the repressor is inactive, when a corepressor (like trp) bind to the repressor, it activates it and the repressor binds to the operator and transcription turns off. |
| explain a positive control operon | an activator portion must bind to DNA to help RNA polymerase start transcription. when the activator Is active (often by binding a ligand) transcription in increase or turned on. |
| main levels where gene expression is regulated in eukaryotes | transcription, RNA processing, translation, post translation |
| what do general transcription factors do | bind to promoter and help RNA polymerase initiate transcription |
| how do repressors inhibit transcription in eukaryotes | block activator binding and interfere with RNA polymerase/activator interaction |
| how does rna interference (RNAi) regulate gene expression | small RNA molecules bind mRNA and degrade it or block transcription |
| what causes lactase persistance | mutation in an enhancer region that keeps the gene turned on |
| lactase peristance | continued expression of the lactase gene into adulthood |
| whys lactase persistence an example of evolution | natural selection favored individuals who could digest milk in dairy farming populations |
| at what level is the lactase gene primarily regulated | transcription |
| 5 main levels of gene expression control | chromosomes (epigenetic) transcriptional rna processing translational post translational |
| TATA box | promoter sequence that helps position RNA polymerase |
| what do siRNA do | bind to mRNA and cause degradation |
| what do miRNA do | bind to mRNA and block translation |
| what does lactose do in a lac operon | inactivates repressor and turns transcription on |
| when the trp operon on | when trp is low |
| whys gene regulation important | allows cells to- respond to environment differentiate (cell types) avoid wasting energy |
Created by:
Lilyhowes